Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
It is known that high bandwidth amplifiers, whose range of coverage spans several tens of GHz, have many applications in wideband RF receivers, because they enable the simultaneous reception of signals transmitted on many frequencies. A popular design choice in such applications is the distributed amplifier.
Integrated circuit (IC) based Radio Frequency (RF) amplifiers are used in many transmitter and receiver systems for the amplification and filtering of RF signals sometimes exceeding frequencies of several tens of Giga Hertz. Such amplifiers are often used together with other external components, such as, capacitors, inductors, mixers, filters, diplexers, etc. on a printed circuit board (PCB) assembly.
A typical configuration of integrated circuit based complementary metal-oxide semiconductor (CMOS) amplifier 110 assembled on a PCB assembly 100 is shown in FIG. 1A. On the integrated circuit interface, a wire-bond 102 connects a bond pad on the IC 104 to a corresponding pad on the PCB 106. This electrical connection is then continued on, using a trace on the PCB 108. As shown in FIG. 1B, several such ICs 152-1, 152-2 may be connected on the PCB assembly 150, along with other components such as mixers 154, filters 156 and diplexers 158. Every IC or component on the PCB assembly is connected to interconnecting traces using wire-bonds and pads as described in FIG. 1A. In one embodiment, the PCB (100) may be replaced by a substrate in an integrated circuit package, with the external connections (102, 104, 106, 108) remaining the same. These connections result in additional capacitance, inductance and resistance being added to the amplifier interface, which greatly degrade its high frequency performance metrics such as gain, bandwidth and power reflections.
Distributed amplifiers that incorporate transmission line theory into traditional amplifier design to obtain a larger gain-bandwidth product than is realizable by conventional circuits, are commonly used for broadband amplifiers. The distributed amplifier work on the principle of delaying an incoming signal and passing it through individual gain stages, and combining all the corresponding outputs to provide gain and a very large bandwidth. Its biggest shortcoming is that if the terminations or resistive loads do not provide appropriate matching for the traveling waves, the performance gets severely degraded due to reflections. As shown in FIG. 1A, the wire-bonds and the interface pads (also known as package parasitics) result in such reflections, resulting in severe performance impairment.
The extent of performance degradation of a typical CMOS based 5 stage distributed amplifier due to package parasitics is apparent from FIG. 2 which illustrates simulation results of a distributed amplifier in absence of package parasitic (curve 202) and in presence of parasitic elements (curve 204). It is apparent from curve 202 and 204 that in absence of package parasitic gain ‘s21’ is 5 dB at 17 GHz, while in presence of parasitic elements, the gain falls to 0 dB at that frequency. Equivalently, the bandwidth for 5 dB or more decreases from 17 GHz to 10 GHz. This is considered significant performance degradation in a wideband RF communication system.
There is therefore a need for a wideband RF amplifier circuit that is easy to implement and the where high frequency performance is not affected due to the impact of external parasitic elements.
All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.